U.S. patent application number 14/156184 was filed with the patent office on 2014-05-15 for method and apparatus for non-access stratum message processing during handover in evolved network.
This patent application is currently assigned to Huawei Technologies Co., Ltd.. The applicant listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Ying HUANG, Yong QIU, Qiang WANG, Hongzhuo ZHANG.
Application Number | 20140133459 14/156184 |
Document ID | / |
Family ID | 40350395 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140133459 |
Kind Code |
A1 |
ZHANG; Hongzhuo ; et
al. |
May 15, 2014 |
METHOD AND APPARATUS FOR NON-ACCESS STRATUM MESSAGE PROCESSING
DURING HANDOVER IN EVOLVED NETWORK
Abstract
A method and an apparatus for non-access stratum (NAS) message
processing during handover in an evolved network are provided. The
method includes the following steps. An evolved packet core (EPC)
receives a message which indicates that a UE is being handed over
sent by a source evolved NodeB (S-eNB), and stops sending an NAS
message to the UE temporarily. The EPC receives a message which
indicates that the UE returns to an S-eNB service area sent by the
S-eNB. The EPC sends the NAS message to the UE through the S-eNB,
if needed. With the method and the apparatus, the EPC can acquire a
location of the UE in time in the case of a handover failure of the
UE, a time limit of a retransmission timer is set precisely, and a
specific implementation for forwarding an NAS message through an X2
interface is provided.
Inventors: |
ZHANG; Hongzhuo; (Shanghai,
CN) ; QIU; Yong; (Shenzhen, CN) ; HUANG;
Ying; (Shanghai, CN) ; WANG; Qiang; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
|
CN |
|
|
Assignee: |
Huawei Technologies Co.,
Ltd.
Shenzhen
CN
|
Family ID: |
40350395 |
Appl. No.: |
14/156184 |
Filed: |
January 15, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12704906 |
Feb 12, 2010 |
8665820 |
|
|
14156184 |
|
|
|
|
PCT/CN2008/071970 |
Aug 13, 2008 |
|
|
|
12704906 |
|
|
|
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Current U.S.
Class: |
370/331 |
Current CPC
Class: |
H04W 36/02 20130101;
H04W 36/0005 20130101; H04W 92/20 20130101; H04W 36/0079 20180801;
H04W 92/12 20130101 |
Class at
Publication: |
370/331 |
International
Class: |
H04W 36/00 20060101
H04W036/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2007 |
CN |
200710140567.9 |
Aug 23, 2007 |
CN |
200710147031.X |
Nov 29, 2007 |
CN |
200710194669.9 |
Claims
1. A method for processing a Non-access Stratum (NAS) message
during a handover of a user equipment (UE) in an evolved network,
the method comprising: receiving, by an Evolved Packet Core (EPC),
a message sent from an source eNodeB (S-eNB), the message
indicating that the UE is in the handover; starting, by the EPC, a
retransmission timer; and sending, by the EPC, the NAS message to
the UE through the S-eNB when the handover fails and the
retransmission timer expires.
2. The method of claim 1, further comprising: stopping, by the EPC,
the retransmission timer after receiving a handover complete
message sent by a target eNodeB (T-eNB); and sending, by the EPC,
the NAS message to the UE through the T-eNB.
3. The method of claim 1, comprising: sending, by the EPC, a
direct-transfer message to the S-eNB before the EPC receives the
message indicating that the UE is in the handover, wherein the
direct-transfer message including the NAS message.
4. The method of claim 3, wherein the message indicating that the
UE is in the handover includes a cause value and the NAS message,
the cause value indicating the NAS message has not been sent to the
UE during the handover and the NAS message that has not been
sent.
5. A Mobility Management Entity (MME), comprising: a receiver,
configured to receive a message sent from an source eNodeB (S-eNB),
wherein the message indicates that a user equipment (UE) is in a
handover; a processor, configured to start a retransmission timer;
and a transmitter, configured to send a Non-access Stratum (NAS)
message to the UE through the S-eNB when the handover fails and the
retransmission timer expires.
6. The MME of claim 5, wherein the processor is further configured
to stop the retransmission timer after the receiver receives a
handover complete message sent by a target eNodeB (T-eNB); and
wherein the transmitter is further configured to send the NAS
message to the UE through the T-eNB.
7. The MME of claim 5, wherein the transmitter is further
configured to send a direct-transfer message to the S-eNB before
the receiver receives the message that indicates that the UE is in
the handover, wherein the direct-transfer message including the NAS
message.
8. The MME of claim 7, wherein the message that indicates that the
UE is in the handover includes a cause value and the NAS message,
wherein the cause value indicates that the NAS message has not been
sent to the UE during the handover and the NAS message that has not
been sent.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/704,906, filed on Feb. 12, 2010, which is a
continuation of International Patent Application No.
PCT/CN2008/071970, filed on Aug. 13, 2008, which claims priority to
Chinese Patent Application No. 200710194669.9, filed on Nov. 29,
2007, Chinese Patent Application No. 200710140567.9, filed on Aug.
13, 2007, and Chinese Patent Application No. 200710147031.X, filed
on Aug. 23, 2007, all of which are hereby incorporated by reference
in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of communication,
and more particularly to a method and an apparatus for non-access
stratum (NAS) message processing during handover in an evolved
network.
BACKGROUND OF THE INVENTION
[0003] The Universal Mobile Telecommunications System (UMTS) is a
third generation mobile communication system adopting a Wideband
Code Division Multiple Access (WCDMA) air interface technique, and
the UMTS adopts a structure similar to that of the second
generation mobile communication system, including a Radio Access
Network (RAN), a Core Network (CN), and User Equipment (UE). The
RAN is configured to process all functions associated with wireless
communication. The CN is configured to process all speech calling
and data connection functions in the UMTS, and perform switching
and routing functions with external networks. The RAN in the UMTS
system is a UMTS Territorial Radio Access Network (UTRAN).
[0004] FIG. 1 is a schematic structural view of a UMTS. The UTRAN
includes one and more Radio Network Subsystems (RNSs), in which
each RNS is formed by one Radio Network Controller (RNC) and one or
more NodeBs. Each RNC is connected with the CN via an Iu interface,
each NodeB is connected with the RNC via an Iub interface, and the
RNCs are interconnected with each other via an Iur interface. Each
RNC is configured to allocate and control wireless resources of the
NodeBs connected with the RNC or associated with the RNC, and each
NodeB is configured to perform a data stream conversion between the
Iub interface and a Uu interface, and meanwhile is participated in
part of the wireless resource management.
[0005] The network architecture shown in FIG. 1 is based on the
architecture of a version earlier than 3GPP Release 6. Considering
the competition capability of the network in the future, the 3GPP
has been researching on a brand new evolved network architecture to
satisfy the application requirements of a mobile network in the
future, which includes a system architecture evolvement (SAE) and a
long time evolvement (LTE) of the access network, and the network
evolvement aims at providing a totally IP-based network with a low
delay, high data rate, high system capacity and coverage, and low
cost.
[0006] FIG. 2 is a schematic architectural view of an evolved
network. The network architecture includes a UE, an Evolved UMTS
Territorial Radio Access Network (E-UTRAN), and an Evolved Packet
Core (EPC). The E-UTRAN is formed by eNodeBs, in which the eNodeBs
are connected with each other via an X2 interface. The EPC includes
a Mobility Management Entity (MME), a serving SAE gateway, and a
Packet Date Network SAE gateway (PDN SAE gateway). The MME is
responsible for the mobility management of a control plane,
including managing user context and mobility status, assigning a
user temporal identifier (ID), and the like. The MME is connected
with a Serving GPRS Support Node (SGSN) in an existing network via
an S3 interface, connected with the E-UTRAN via an S1-MME
interface, and with the Serving SAE Gateway via an S1-U interface.
The MME is configured with a timer therein. The Serving SAE Gateway
is responsible for initiating a paging for a downlink data in Idle
state, managing and saving IP bearer parameters and routing
information in a network, and the like. The PDN SAE gateway serves
as a user plane anchor point among different access systems. The
system shown in FIG. 2 further includes a Policy and Charging Rule
Function (PCRF) and a Home Subscriber Server (HSS).
[0007] In the evolved network architecture, a handover of X2
interfaces exists between the eNodeBs. If an eNodeB where the UE is
currently located is called a Source eNodeB (S-eNB), and an eNodeB
where the UE will be handed over to is called a Target eNodeB
(T-eNB), the above handover refers a process that the UE is handed
over from the S-eNB to a cell controlled by the T-eNB.
[0008] In actual applications, the EPC needs to send an NAS message
to the UE through the eNodeB to realize a service corresponding to
the UE, in which the time point and time interval for sending the
NAS message vary with different services. In the prior art, there
is a solution for NAS message processing if the handover is
successful. Unfortunately, if the handover fails, no technical
solution is available for enabling the EPC to send the NAS message
to the UE.
[0009] Therefore, in the solution for NAS message processing in the
prior art, the EPC cannot be informed timely if the handover fails,
that is, the UE returns to an S-eNB service area again, and as a
result, the EPC cannot correctly send the NAS message to the
UE.
SUMMARY OF THE INVENTION
[0010] Accordingly, the embodiments of the present invention are
directed to a method for NAS message processing during handover in
an evolved network, an eNodeB, and an MME.
[0011] An embodiment of the present invention provides a method for
NAS message processing during handover in an evolved network, which
includes the following steps.
[0012] An EPC sends a direct-transfer message to an S-eNB, in which
the direct-transfer message contains an NAS message sent to a UE by
the EPC.
[0013] The EPC receives a message, which indicates that the UE is
being handed over, sent by the S-eNB.
[0014] The message which indicates that the UE is being handed over
is a direct transfer failure message or a direct transfer response
message containing a cause value and the NAS message that fails to
be sent.
[0015] An embodiment of the present invention provides a method for
NAS message processing during handover in an evolved network, which
includes the following steps.
[0016] An EPC receives a message which, indicates that a UE is
being handed over, sent by an S-eNB, and buffers an NAS message to
be sent to the UE.
[0017] If the handover fails, the EPC receives a message, which
indicates that the UE returns to an S-eNB service area, sent by the
S-eNB.
[0018] When it is necessary to send the NAS message to the UE, the
EPC sends the NAS message to the UE through the S-eNB.
[0019] An embodiment of the present invention provides a method for
NAS message processing during handover in an evolved network, in
which a retransmission timer is configured, and the method includes
the following steps.
[0020] An EPC receives a message, which indicates that a UE is
being handed over, sent by an S-eNB, and starts the retransmission
timer.
[0021] If the handover fails, when it is necessary to send an NAS
message to the UE after the retransmission timer expires, the EPC
sends the NAS message to the UE through the S-eNB.
[0022] An embodiment of the present invention provides an MME in an
EPC, and the MME includes a message transceiver module and an
execution module.
[0023] The message transceiver module is configured to receive a
message, which indicates that a UE is being handed over, sent by an
S-eNB, and transmit the message to the execution module; receive a
message, which indicates that the UE returns to an S-eNB service
area, sent by the S-eNB, and transmit the message to the execution
module, if the handover fails.
[0024] The execution module is configured to receive the message,
which indicates that the UE is being handed over, transmitted by
the message transceiver module, buffer an NAS message to be sent to
the UE; receive the message, which indicates that the UE returns to
the S-eNB service area, transmitted by the message transceiver
module, and send to the S-eNB the NAS message to be sent to the UE
when it is necessary to send the NAS message to the UE.
[0025] An embodiment of the present invention provides an MME in an
EPC, and the MME includes a retransmission timer, a control module,
and an execution module.
[0026] The control module is configured to receive a message, which
indicates that a UE is being handed over, sent by an S-eNB, and
start the retransmission timer; receive a handover complete message
sent by a T-eNB, and stop the retransmission timer.
[0027] The execution module is configured to resolve a timing
result of the retransmission timer, and send an NAS message to the
S-eNB when it is necessary to send the NAS message to the UE after
the retransmission timer expires, or send the NAS message to the
T-eNB when it is necessary to send the NAS message to the UE after
the retransmission timer is stopped.
[0028] An embodiment of the present invention provides an eNodeB,
which includes a detecting module, an NAS message forwarding
module, and a handover processing module.
[0029] The detecting module is configured to detect an abnormal
status during handover of a UE, and send a detecting result to the
handover processing module.
[0030] The handover processing module is configured to send a
message to an EPC which indicates that the UE is being handed over,
and send to the EPC a message about a NodeB service area where the
UE is currently located according to the detecting result sent by
the detecting module when the handover of the UE fails.
[0031] The NAS message forwarding module is configured to receive
an NAS message sent by the EPC, and forward the message to the
UE.
[0032] An embodiment of the present invention provides an MME,
which includes a message sending module and a message receiving
module.
[0033] The message sending module is configured to be used by the
EPC to send a direct-transfer message to an S-eNB, in which the
direct-transfer message contains an NAS message to be sent to the
UE by the EPC.
[0034] The message receiving module is configured to receive a
message which indicates that the UE is being handed over sent by
the S-eNB, in which the message which indicates that the UE is
being handed over is a direct transfer failure message or a direct
transfer response message containing a cause value and the NAS
message that fails to be sent.
[0035] In view of the above, with the method for NAS message
processing during handover in an evolved network, the eNodeB, and
the MME provided in the embodiments of the present invention, an
EPC sends a direct-transfer message to an S-eNB, and the
direct-transfer message contains an NAS message to be sent by the
EPC to a UE. The S-eNB notifies the EPC that a message about the UE
being currently handed over contains the NAS message that fails to
be sent by the S-eNB to the UE, so that the EPC only needs to
buffer the NAS message when the NAS message fails to be
transferred, so as to reduce the occupied EPC storage space.
Alternatively, the S-eNB notifies the EPC that the UE is currently
being handed over and notifies the EPC to buffer the NAS message to
be sent to the UE. When the handover fails, the S-eNB sends a
message which indicates that the UE returns to an S-eNB service
area to the EPC, so as to enable the EPC to correctly send the NAS
message to the UE. Alternatively, a retransmission timer is set and
adopted. When the handover fails, the EPC correctly sends the NAS
message to the UE through the S-eNB after the retransmission timer
expires, and when the handover is successful, the EPC stops the
retransmission timer, and correctly sends the NAS message to the UE
through a T-eNB.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a schematic structural view of a UMTS system;
[0037] FIG. 2 is a schematic architectural view of an evolved
network;
[0038] FIG. 3 is a schematic flowchart of a first method for NAS
message processing during handover in an evolved network according
to an embodiment of the present invention;
[0039] FIG. 4 is a schematic flowchart of a first preferred
embodiment of the flow shown in FIG. 3;
[0040] FIG. 5 is a schematic flowchart of a second preferred
embodiment of the flow shown in FIG. 3;
[0041] FIG. 6 is a schematic flowchart of the flow, when the
handover is successful, included in the flow shown in FIG. 3;
[0042] FIG. 7 is a schematic flowchart of a second method for NAS
message processing during handover in an evolved network according
to an embodiment of the present invention;
[0043] FIG. 8 is a schematic flowchart of a preferred embodiment of
the flow shown in FIG. 7;
[0044] FIG. 9 is a schematic flowchart of a method for NAS message
processing during handover in an evolved network according to an
embodiment of the present invention;
[0045] FIG. 10 is a schematic flowchart of a first preferred
embodiment of the flow show in FIG. 9;
[0046] FIG. 11 is a schematic flowchart of a second preferred
embodiment of the flow shown in FIG. 9;
[0047] FIG. 12 is a schematic flowchart of a T-eNB further
receiving an NAS message sent by an S-eNB via a tunnel in the flow
shown in FIG. 9;
[0048] FIG. 13 is a schematic flowchart of a first preferred
embodiment of the flow shown in FIG. 12;
[0049] FIG. 14 is a schematic flowchart of a second preferred
embodiment of the flow shown in FIG. 12;
[0050] FIG. 15 is a schematic flowchart of the first preferred
embodiment of the S-eNB sending an NAS message to a UE when the
handover fails in the flow shown in FIG. 12;
[0051] FIG. 16 is a schematic flowchart of the second preferred
embodiment of the S-eNB sending an NAS message to a UE when the
handover fails in the flow shown in FIG. 12;
[0052] FIG. 17 is a schematic structural view of a first type of
MME in an EPC according to an embodiment of the present
invention;
[0053] FIG. 18 is a schematic structural view of a second type of
MME in an EPC according to an embodiment of the present
invention;
[0054] FIG. 19 is a schematic structural view of a first eNodeB
according to an embodiment of the present invention;
[0055] FIG. 20 is a schematic structural view of a second eNodeB
according to an embodiment of the present invention;
[0056] FIG. 21 is a schematic structural view of a third eNodeB
according to an embodiment of the present invention; and
[0057] FIG. 22 is a schematic structural view of another MME
according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0058] In order to make the objectives and advantages of the
embodiments of the present invention more comprehensible, the
embodiments of the present invention are illustrated below in
detail with reference to the accompanying drawings
[0059] Firstly, a method for NAS message processing during handover
in an evolved network according to an embodiment of the present
invention is illustrated, which includes two specific methods.
[0060] FIG. 3 is a schematic flowchart of a first method for NAS
message processing during handover in an evolved network according
to an embodiment of the present invention, which includes the
following steps.
[0061] In step 601, an EPC receives a message, which indicates that
a UE is being handed over, sent by an S-eNB, and buffers an NAS
message to be sent to the UE.
[0062] In this step, before the EPC receives the message sent by
the S-eNB, this step further includes that the EPC sends a
direct-transfer message to the S-eNB, where the direct-transfer
message contains the NAS message to be sent to the UE. In this
case, the message sent by the S-eNB may be a direct transfer
failure message or a direct transfer response message, and the
direct transfer failure message or the direct transfer response
message may contain a cause value, for example, the UE is being
handed over, and may further contain the NAS message received by
the S-eNB from the EPC. The NAS message may be an NAS message
received from the EPC before the S-eNB sends a handover command to
the UE, or an NAS message received from the EPC after the S-eNB
sends a handover command to the UE. Alternatively, after the S-eNB
sends a handover command to the UE, the EPC does not send an NAS
message, and the S-eNB directly sends a handover notification
message to the EPC, and in this case, the EPC directly acquires
that the UE is being handed over.
[0063] If the handover fails, the UE returns to an S-eNB service
area, and the S-eNB sends a message which indicates that the UE
returns to the S-eNB service area to the EPC.
[0064] In step 602, if the handover fails, the EPC receives the
message which indicates that the UE returns to the S-eNB service
area sent by the S-eNB.
[0065] In step 603, the EPC sends an NAS message to the UE through
the S-eNB, when it is necessary to send the NAS message to the
UE.
[0066] In this step, after the EPC acquires that the UE currently
returns to the S-eNB service area in step 602, when it is necessary
to send the NAS message to the UE, the EPC sends the NAS message to
the UE through the S-eNB. Considering the sending mode, the EPC
sends to the S-eNB the direct-transfer message containing the NAS
message to be sent to the UE by the EPC, and then the S-eNB sends
the NAS message to the UE by using a Radio Resource Control (RRC)
message downlink direct-transfer message.
[0067] Through step 601-step 603, the flow of the first method for
NAS message processing during handover in an evolved network
according to an embodiment of the present invention is ended. In
this flow, the S-eNB sends a handover command to the UE, that is,
the NAS message processing manner after the handover begins.
[0068] The specific interaction processes involved during the
handover, for example, sending, by the S-eNB, a handover request to
a T-eNB, and performing, by the T-eNB, an admission control, all
belong to the common sense for those of ordinary skill in the art,
which are not repeated in the above method of the embodiment of the
present invention and the subsequent descriptions.
[0069] In the first method for NAS message processing during
handover in an evolved network according to an embodiment of the
present invention, when the handover fails, the EPC receives the
message, which indicates that the UE returns to the S-eNB service
area, sent by the S-eNB, and since the EPC has acquired the exact
position of the UE currently, when it is necessary to send the NAS
message to the UE, the EPC sends the NAS message to the UE through
the S-eNB, thereby realizing the effect of sending the NAS message
correctly to the UE when the handover fails.
[0070] FIG. 4 is a schematic flow chart of a first preferred
embodiment of the flow shown in FIG. 3, which shows a complete
process from sending, by the S-eNB, the handover command to the UE
till the NAS message processing after the handover begins. The flow
shown in FIG. 4 includes the following steps.
[0071] In step 701, the UE receives a handover command message sent
by the S-eNB, and the message instructs the UE to complete the
handover process.
[0072] In step 702, the EPC sends the direct-transfer message to
the S-eNB, and the direct-transfer message contains the NAS message
to be sent to the UE.
[0073] In step 703, the S-eNB founds that the UE is no longer
located in a service area of the S-eNB, and the S-eNB sends the
direct transfer failure message or direct transfer response message
to the EPC. The direct transfer failure message or direct transfer
response message contains a cause value, for example, the UE is
being handed over, and may further contain the NAS message received
by the S-eNB from the EPC. The NAS message may be received from the
EPC before the S-eNB sends a handover command to the UE, or may be
received from the EPC after the S-eNB sends a handover command to
the UE.
[0074] In step 704, the EPC buffers the sending of the NAS message
after receiving the direct transfer failure message or direct
transfer response message.
[0075] In step 705, the S-eNB detects that the handover fails, or
detects other abnormal situations.
[0076] In step 706, the S-eNB initiates a handover canceling flow
to the T-eNB.
[0077] In step 707, the S-eNB sends a message containing a current
position of the UE to the EPC, that is, notifies the EPC that the
UE returns to the S-eNB service area.
[0078] In step 708, the EPC sends to the S-eNB the NAS message to
be sent to the UE when it is necessary to send the NAS message to
the UE.
[0079] In step 709, the S-eNB forwards the NAS message sent by the
EPC to the UE by using an RRC message downlink direct-transfer
message.
[0080] Step 702 may be performed before step 701, that is, there is
no strict sequence relation between step 701 and step 702.
[0081] Step 706 may be an optional step, that is, this embodiment
may not include step 706. If step 706 is included, there is no
strict sequence relation between step 706 and step 707 during
execution.
[0082] In step 707, the message containing the current position of
the UE sent by the S-eNB to the EPC may be an existing 51 interface
message, or may be a new message, as long as the message can be
adopted to notify the EPC that the UE returns to the S-eNB service
area currently. Table 1 shows a format of the above message.
TABLE-US-00001 TABLE 1 Type Cell/Group Name Reference Symbol
Description Message Type Mandatory MME Application Part Mandatory
Integer, Indicating a receiving Protocol Identifier String end of
messages ENodeB Identifier Mandatory Integer, Indicating identifier
of String the eNodeB itself Cause Optional Integer, Indicating a
cause value Enumerated
[0083] In this preferred embodiment, the S-eNB sends the message
containing the current position of the UE to the EPC, so that the
EPC is able to acquire the position of the UE correctly when the
handover fails.
[0084] FIG. 5 is a schematic flow chart of a second preferred
embodiment of the flow shown in FIG. 3, which shows a process from
initiating the handover till finishing the NAS message processing
after the handover begins. The flow shown in FIG. 5 includes the
following steps.
[0085] Step 801 is the same as step 701.
[0086] In step 802, the S-eNB sends a handover notification message
to the EPC, so as to notify the EPC that the UE is currently being
handed over.
[0087] In step 803, the EPC buffers the sending of the NAS message
after receiving the handover notification message.
[0088] Steps 804-808 are respectively the same as steps
705-709.
[0089] Similar to the first preferred embodiment, step 805, in
which the S-eNB initiates a handover canceling flow to the T-eNB,
is an optional step, and there is not strict sequence relation
between step 805 and step 806.
[0090] In step 806, the same as step 707, the message containing
the current position of the UE sent by the S-eNB to the EPC may be
an existing 51 interface message, or may be a new message, as long
as the message can be adopted to notify the EPC that the UE returns
to the S-eNB service area currently. Table 1 shows a format of the
above message.
[0091] In step 802, the handover notification message sent by the
S-eNB to the EPC may have various formats, and Table 2 has listed
one specific format of the above handover notification message.
TABLE-US-00002 TABLE 2 Type Cell/Group Name Reference Symbol
Description Message Type Mandatory MME Application Part Mandatory
Integer, Indicating a receiving Protocol Identifier String end of
messages ENodeB Identifier Mandatory Integer, Indicating the
identifier String of the eNodeB Cause Optional Integer, Indicating
a cause value Enumerated
[0092] The difference between the above flow shown in FIG. 5 and
that shown in FIG. 4 lies in that, in the flow shown in FIG. 5, the
S-eNB directly notifies the EPC that the UE is being handed over,
rather than sending the direct transfer failure message or direct
transfer response message to notify the EPC that the UE is being
handed over after the EPC sends the direct-transfer message. Thus,
when the handover fails, the S-eNB directly notifies the EPC of the
current position of the UE, which is much simpler than the mode of
first receiving the direct transfer message sent by the EPC and
then returning the direct transfer failure message or direct
transfer response message to notify the EPC of the current position
of the UE.
[0093] The flow shown in FIG. 3 may further include the processing
flow when the handover is successful. FIG. 6 shows a complete
processing flow when the handover is successful. The flow includes
the following steps.
[0094] Steps 901-903 are the same as steps 801-803.
[0095] In step 904, the UE sends a handover acknowledgement message
to the T-eNB, so as to indicate that the handover is completed.
[0096] In step 905, the T-eNB sends a handover complete message to
the EPC, so as to notify the EPC that the UE has completed the
handover.
[0097] In step 906, the EPC sends the direct-transfer message to
the T-eNB when it is necessary to send the NAS message to the UE,
and the direct-transfer message contains the NAS message to be sent
to the UE.
[0098] In step 907, the T-eNB sends the NAS message to the UE by
using an RRC downlink direct-transfer message.
[0099] Different from the handover failure situation, if the above
handover is successful, the T-eNB sends a handover complete message
to the EPC, which is equivalent to notifying the EPC that the UE
enters a T-eNB service area currently, so as to instruct the EPC to
send the NAS message to the UE through the T-eNB.
[0100] The flows of two preferred embodiments of the above first
method for NAS message processing during handover in an evolved
network according to an embodiment of the present invention have
been described above.
[0101] FIG. 7 is a schematic flow chart of a second method for NAS
message processing during handover in an evolved network according
to an embodiment of the present invention. The flow includes the
following steps.
[0102] In step 1001, an EPC receives a message, which indicates
that a UE is being handed over, sent by an S-eNB, and starts a
retransmission timer.
[0103] In this step, before the EPC receives the message sent by
the S-eNB, this step further includes that the EPC sends a
direct-transfer message to the S-eNB, and the direct-transfer
message contains an NAS message to be sent to the UE. In this case,
the message sent by the S-eNB may be a direct transfer failure
message or direct transfer response message. The direct transfer
failure message or direct transfer response message may contain a
cause value, for example, the UE is being handed over, and may
further contain the NAS message received by the S-eNB from the EPC.
The NAS message may be received from the EPC before the S-eNB sends
a handover command to the UE, or may be received from the EPC after
the S-eNB sends a handover command to the UE.
[0104] The receiving, by the EPC, the message sent by the S-eNB may
further includes receiving, by the EPC, a handover notification
message directly sent by the S-eNB without sending a
direct-transfer message by the EPC, and in this case, the EPC
directly acquires that the UE is being handed over. In this step,
the started retransmission timer may be an S1 application part
(S1-AP) protocol retransmission timer, or may be another
retransmission timer.
[0105] In step 1002, if the handover is successful, the EPC
receives the handover complete message sent by the T-eNB, stops the
retransmission timer, and sends the NAS message to the UE through
the T-eNB when it is necessary to send the NAS message to the
UE.
[0106] In step 1003, if the handover fails, when it is necessary to
send the NAS message to the UE after the retransmission timer
expires, the EPC sends the NAS message to the UE through the
S-eNB.
[0107] In this step, if the EPC does not receive the handover
complete message from the UE after the retransmission timer
expires, it is considered that the UE is still located in the S-eNB
service area. In this case, when it is necessary to send the NAS
message to the UE, the EPC sends the NAS message to the UE through
the S-eNB. Considering the sending mode, the EPC sends to the S-eNB
a direct-transfer message containing the NAS message to be sent to
the UE, and then the S-eNB sends the NAS message to the UE by using
an RRC message downlink direct-transfer message.
[0108] In the second method for NAS message processing during
handover in an evolved network according to an embodiment of the
present invention, a retransmission timer is disposed in the EPC,
and when the handover fails, the EPC can correctly send the NAS
message to the UE when it is necessary to send the NAS message to
the UE after the retransmission timer expires. When the handover is
successful, the EPC stops the retransmission timer after receiving
the handover complete message, and then sends the NAS message
through the T-eNB.
[0109] In step 1001, the message which indicates that the UE is
being handed over received by the EPC may further contain time
information. If the time is synchronous between the S-eNB and the
EPC, the time information may be a time point when the S-eNB sends
the handover command to the UE, or a time point when the S-eNB
receives the direct-transfer message, or returns the direct
transfer failure message, and the like. If the time is asynchronous
between the S-eNB and the EPC, the time information may be a time
interval between sending the handover command to the UE and
receiving the direct-transfer message by the S-eNB. In this case,
in step 1001, a time limit of the retransmission timer may be
determined according to the time information, and then the
retransmission timer is started, so as to accurately determine the
time limit of the retransmission timer.
[0110] A preferred embodiment is provided for the second method for
NAS message processing during handover in an evolved network. FIG.
8 shows a flow of a preferred embodiment of the flow shown in FIG.
7, which is a processing flow when the handover fails, and includes
the following steps.
[0111] In step 1101, the UE receives a handover command message
sent by the S-eNB, and the message instructs the UE to complete the
handover process.
[0112] In step 1102, the EPC sends the direct-transfer message to
the S-eNB, and the direct-transfer message contains the NAS message
to be sent to the UE.
[0113] In step 1103, the S-eNB found that the UE is no longer
located in a service area of the S-eNB, and sends the direct
transfer failure message or direct transfer response message to the
EPC, and the direct transfer failure message or direct transfer
response message contains a cause value and time information. The
direct transfer failure message or direct transfer response message
may further contain the NAS message received by the S-eNB from the
EPC. The NAS message may be received from the EPC before the S-eNB
sends a handover command to the UE, or may be received from the EPC
after the S-eNB sends a handover command to the UE.
[0114] In step 1104, if the message contains the time information,
according to the time information carried in the direct transfer
failure message or direct transfer response message and based on
the experience value, the EPC determines a time length of the
handover process of the UE, thus determining a time limit of the
retransmission timer, starting the retransmission timer, and
stopping sending the NAS message temporarily.
[0115] In step 1105, the S-eNB detects that the handover fails, or
detects other abnormal situations.
[0116] In step 1106, the S-eNB initiates a handover canceling flow
to the T-eNB.
[0117] In step 1107, the retransmission timer in the EPC
expires.
[0118] In step 1108, when it is necessary to send the NAS message
to the UE, the EPC sends the direct-transfer message to the S-eNB,
and the direct-transfer message contains the NAS message to be sent
to the UE.
[0119] In step 1109, the S-eNB sends the NAS message to the UE by
using an RRC message downlink direct-transfer message.
[0120] Step 1102 may be performed before step 1101, that is, there
is no strict sequence relation between step 1101 and step 1102.
[0121] Step 1106 is an optional step, and there is no strict
sequence relation between step 1106 and steps 1107-1108.
[0122] In step 1103, the direct transfer failure message or direct
transfer response message sent to the EPC by the S-eNB not only
contains the cause value, but also contains the time information. A
message format of the direct transfer failure message or direct
transfer response message is listed in Table 3.
TABLE-US-00003 TABLE 3 Type Cell/Group Name Reference Symbol
Description Message Type Mandatory MME Application Part Mandatory
Integer, Indicating a receiving Protocol Identifier String end of
messages ENodeB Identifier Optional Integer, Indicating the
identifier String of the eNodeB Cause Optional Integer, Cause value
Enumerated Time Information Mandatory Integer, Time information
String Time Stamp Optional Integer, Time stamp String Time Interval
Optional Integer Time interval
[0123] Similarly, in the flow shown in FIG. 8, after the UE begins
to be handed over, the S-eNB directly notifies the EPC that the UE
is currently being handed over, rather than receiving the
direct-transfer message sent by the EPC and then notifying the EPC
that the UE is currently handed over through the direct transfer
failure message or direct transfer response message. Thus, the flow
is simplified.
[0124] Next, a method for forwarding an NAS message during handover
in an evolved network according to an embodiment of the present
invention is described below.
[0125] FIG. 9 is a schematic flow chart of a method for NAS message
processing during handover in an evolved network according to an
embodiment of the present invention. The flow includes the
following steps.
[0126] In step 1201, an S-eNB receives an NAS message sent by an
EPC. The NAS message may be received from the EPC before the S-eNB
sends a handover command message to a UE, or received from the EPC
after the S-eNB sends a handover command message to the UE.
[0127] In step 1202, a T-eNB receives the NAS message sent by the
S-eNB by using an X2 interface control protocol message or a
tunnel. The S-eNB may send the NAS message by containing the NAS
message in an RRC message, for example, an RRC downlink
direct-transfer message, or may send the NAS message directly.
[0128] In step 1203, if the handover fails, the S-eNB sends the NAS
message to the UE.
[0129] In step 1204, if the handover is successful, the T-eNB sends
the NAS message to the UE.
[0130] In the method for NAS message processing during handover in
an evolved network according to an embodiment of the present
invention, the NAS message may be borne in the X2 interface control
protocol message, and may be forwarded between the S-eNB and the
T-eNB via the X2 interface control message, or forwarded via a
tunnel between the S-eNB and the T-eNB, which are specific
implementations for forwarding the NAS message at the X2
interface.
[0131] The above X2 interface control protocol message may have
different alternative forms. By taking an X2-AP control protocol
message and a GTP-C control protocol message as examples below, two
preferred embodiments of the first method for NAS message
processing during handover in an evolved network according to an
embodiment of the present invention are described below.
[0132] FIG. 10 is a schematic flow chart of a first preferred
embodiment of the flow shown in FIG. 9. The flow shown in FIG. 10
includes the following steps.
[0133] In step 1301, the UE receives the handover command message
sent by the S-eNB, and the message instructs the UE to complete the
handover process.
[0134] In step 1302, the EPC sends a downlink direct-transfer
message to the S-eNB, and the downlink direct-transfer message
contains the NAS message to be sent to the UE.
[0135] In step 1303, the S-eNB sends the received NAS message to
the T-eNB. Specifically, the S-eNB sends the received NAS message
to the T-eNB in a cell format by bearing the NAS message in the
X2-AP control protocol message. The S-eNB forwards the NAS message
by containing the NAS message in an RRC message, for example, an
RRC downlink direct-transfer message, or forwards the NAS message
directly.
[0136] In step 1304, the UE sends a handover acknowledgement
message to the T-eNB.
[0137] In step 1305, the T-eNB sends a handover complete message to
the EPC, so as to notify the EPC that the UE has completed the
handover process.
[0138] In step 1306, the EPC sends a handover complete response
message to the T-eNB, so as to confirm that the handover is
completed.
[0139] In step 1307, the T-eNB sends the NAS message to the UE by
using the RRC downlink direct-transfer message.
[0140] In the flow shown in FIG. 10, step 1302 may be performed
before step 1301.
[0141] In the flow shown in FIG. 10, step 1307 may be performed
immediately after step 1304 or step 1305.
[0142] The X2-AP control protocol message in step 1303 may be an
application layer message exclusively added at the X2 interface,
and a message format of such message is listed in Table 4.
TABLE-US-00004 TABLE 4 Type Cell/Group Name Reference Symbol
Description Message Type Mandatory S-eNB Identifier Mandatory
Indicating a receiving end of messages T-eNB Identifier Mandatory
Indicating identifier of the T-eNB itself NAS Message Mandatory
String Indicating forwarded NAS message
[0143] FIG. 11 is a schematic flow chart of a second embodiment of
the flow shown in FIG. 9. The flow shown in FIG. 11 includes the
following steps.
[0144] Steps 1401-1402 are the same as steps 1301-1302, and steps
1404-1407 are the same as steps 1304-1307.
[0145] The difference between the flow shown in FIG. 11 and the
flow shown in FIG. 10 lies in that, in step 1403 of FIG. 11, the
S-eNB sends the received NAS message to the T-eNB, and
specifically, the S-eNB sends the received NAS message by bearing
the NAS message in the GTP-C control protocol message. The S-eNB
forwards the NAS message by containing the NAS message in an RRC
message, for example, an RRC downlink direct-transfer message, or
forwards the NAS message directly.
[0146] The GTP-C control protocol message may be a user plane
message exclusively added at the X2 interface, and a message format
of such message is listed in Table 5.
TABLE-US-00005 TABLE 5 Type Cell/Group Name Reference Symbol
Description Message Type Mandatory Indicating an identifier of a
newly-added GTP-C message NAS message Mandatory Binary Indicating a
forwarded NAS String message
[0147] In the flow shown in FIG. 9, the T-eNB may further receive
the NAS message sent by the S-eNB via a tunnel. FIG. 12 is a
schematic flow chart of the flow shown in FIG. 9, in which a T-eNB
further receives an NAS message sent by an S-eNB via a tunnel. The
flow shown in FIG. 12 includes the following steps.
[0148] In step 1501, the T-eNB sends a user plane IP address and a
tunnel end point identifier corresponding to the T-eNB to the
S-eNB, and establishes a tunnel from the S-eNB to the T-eNB.
[0149] In step 1502, the T-eNB receives the NAS message sent by the
S-eNB via the established tunnel. The S-eNB may forward the NAS
message by containing the NAS message in an RRC message, for
example, an RRC downlink direct-transfer message, or forward the
NAS message directly.
[0150] In step 1503, if the handover is successful, the T-eNB sends
the NAS message to the UE.
[0151] The established tunnel may be a tunnel exclusively
configured to forward an NAS message, or may be a tunnel configured
to transmit user data, which is shared for forwarding the NAS
message. The difference there-between lies in that, the tunnel end
point identifier sent by the S-eNB to the T-eNB when the tunnel is
established is a tunnel end point identifier configured to forward
the NAS message or a tunnel end point identifier configured to
transmit the user data. Thus, depending upon different tunnel end
point identifiers, different tunnels are respectively established.
By taking the above two tunnels as examples, two preferred
embodiments of the second method for NAS message processing during
handover in an evolved network according to an embodiment of the
present invention are illustrated below.
[0152] The above established tunnel is a unidirectional tunnel from
the S-eNB to the T-eNB. If the handover process fails, the T-eNB
may further return the NAS message to the S-eNB, and in this case,
a tunnel from the T-eNB to the S-eNB is further required.
[0153] FIG. 13 is a schematic flow chart of a first preferred
embodiment of the flow shown in FIG. 12. The flow shown in FIG. 13
includes the following steps.
[0154] In step 1601, the S-eNB sends a handover request message to
the T-eNB.
[0155] If the failure of the handover process is considered in this
flow, the T-eNB returns the NAS message to the S-eNB. At this time,
the handover request message in step 1601 may contain a user plane
IP address of the S-eNB and a tunnel end point identifier
configured to forward the NAS message.
[0156] In step 1602, the T-eNB sends a handover request response
message to the S-eNB, and the message contains a user plane IP
address of the T-eNB and a tunnel end point identifier configured
to forward the NAS message.
[0157] Through steps 1601-1602, a NAS forwarding tunnel is
established, which may be a unidirectional tunnel or a
bi-directional tunnel.
[0158] In step 1603, the UE receives the handover command message
sent by the S-eNB, and the message instructs the UE to complete the
handover process.
[0159] In step 1604, the EPC sends a downlink direct-transfer
message to the S-eNB, and the downlink direct-transfer message
contains the NAS message to be sent to the UE.
[0160] In step 1605, the S-eNB sends the NAS message to the T-eNB
via the NAS message forwarding tunnel established through steps
1601 and 1602. The S-eNB may forward the NAS message by containing
the NAS message in an RRC message, for example, an RRC downlink
direct-transfer message, or forward the NAS message directly.
[0161] In step 1606, the UE sends a handover acknowledgement
message to the T-eNB.
[0162] In step 1607, the T-eNB sends a handover complete message to
the EPC, so as to notify the EPC that the UE has completed the
handover process.
[0163] In step 1608, the EPC sends a handover complete response
message to the T-eNB, so as to confirm that the handover is
completed.
[0164] In step 1609, the T-eNB sends the NAS message to the UE by
using an RRC message downlink direct-transfer message.
[0165] Step 1609 may be performed immediately after step 1606 or
step 1607.
[0166] In the above flow, if the handover fails, the T-eNB may
return the NAS message to the S-eNB via the bi-directional tunnel
established through steps 1601-1602, and then the S-eNB sends the
NAS message to the UE.
[0167] FIG. 14 is a schematic flow chart of a second preferred
embodiment of the flow shown in FIG. 12. The flow shown in FIG. 14
includes the following steps.
[0168] In step 1701, the S-eNB sends a handover request message to
the T-eNB.
[0169] If the failure of the handover process is considered in this
flow, the T-eNB returns the NAS message to the S-eNB. At this time,
the handover request message in step 1701 may contain a user plane
IP address of the S-eNB and a tunnel end point identifier for
forwarding the NAS message.
[0170] In step 1702, the T-eNB sends a handover request response
message to the S-eNB, and the message contains a user plane IP
address of the T-eNB and a tunnel end point identifier for
transmitting user data.
[0171] Through steps 1701-1702, a user data transmitting tunnel is
established, which may be a unidirectional tunnel or a
bidirectional tunnel.
[0172] Steps 1703-1704 are the same as steps 1603-1604.
[0173] In step 1705, the S-eNB sends the NAS message to the T-eNB
via the user data transmitting tunnel established through steps
1701 and 1702. The S-eNB may forward the NAS message by containing
the NAS message in an RRC message, for example, an RRC downlink
direct-transfer message, or forward the NAS message directly. Steps
1706-1709 are the same as steps 1606-1609.
[0174] Step 1709 may be performed immediately after step 1706 or
step 1707.
[0175] In the flow shown in FIG. 14, the S-eNB forwards the NAS
message to the T-eNB via the user data transmitting tunnel. Before
the NAS message is forwarded, a label needs to be added to the NAS
message, so as to enable the T-eNB to identify messages transmitted
via the same user data transmitting tunnel, thereby identifying the
user data and the NAS message. The label may be added in various
different ways, for example, adding a label field in a header of
the GTP-U protocol.
[0176] The above user data transmitting tunnel for forwarding the
NAS message may be one of a plurality of user data transmitting
tunnels established between the S-eNB and the T-eNB. When a certain
tunnel is selected for forwarding the NAS message while
transmitting user data, various selection manners may be adopted,
for example, selecting a tunnel according to a sequence, selecting
a tunnel according to load sharing, or selecting a tunnel randomly,
and the like.
[0177] In the above flow, if the handover fails, the T-eNB returns
the NAS message to the S-eNB via the bi-directional tunnel
established through steps 1801-1802, and then the S-eNB sends the
NAS message to the UE.
[0178] In the flow shown in FIG. 12, when the handover fails, the
S-eNB sends the NAS message to the UE, which particularly includes
two implementation modes. FIG. 15 is a schematic flow chart of the
first preferred embodiment of the S-eNB sending an NAS message to a
UE when the handover fails in the flow shown in FIG. 12. The flow
shown in FIG. 15 includes the following steps.
[0179] In step 1801, the S-eNB makes a backup of the NAS message
sent to the UE by the EPC.
[0180] In step 1802, if the handover fails, the S-eNB sends the
backup of the NAS message to the UE.
[0181] In this preferred embodiment, the S-eNB makes a backup of
the NAS message, and when the handover fails, the S-eNB sends the
backup of the NAS message to the UE, thereby realizing the effect
of correctly sending the NAS message to the UE when the handover
fails.
[0182] Before the S-eNB sends the backup of the NAS message to the
UE, the S-eNB initiates a handover canceling flow to the T-eNB.
[0183] FIG. 16 is a schematic flow chart of the second preferred
embodiment of the S-eNB sending an NAS message to a UE when the
handover fails in the flow shown in FIG. 12. The flow shown in FIG.
16 includes the following steps.
[0184] In step 1901, the S-eNB receives the NAS message sent to the
UE by the EPC, and sends the NAS message to the T-eNB.
[0185] In step 1902, if the handover fails, the S-eNB receives the
NAS message sent by the T-eNB.
[0186] In step 1903, the S-eNB sends the NAS message to the UE.
[0187] In this preferred embodiment, when the UE is being handed
over, the S-eNB forwards the received NAS message to the T-eNB. If
the handover fails, the T-eNB further forwards the NAS message back
to the S-eNB, and then the S-eNB sends the NAS message to the UE.
When the handover fails, the NAS message is forwarded between the
S-eNB and the T-eNB, thereby realizing the effect of correctly
sending the NAS message to the UE.
[0188] Before the S-eNB receives the NAS message sent by the T-eNB,
the S-eNB further initiates a handover canceling process to the
T-eNB.
[0189] Next, an apparatus for NAS message processing during
handover in an evolved network according to an embodiment of the
present invention is described below, which includes an eNodeB and
an MME in an EPC, in which the MME in the EPC further includes two
circumstances.
[0190] FIG. 17 is a schematic structural view of a first type of
MME in an EPC according to an embodiment of the present invention.
The MME includes a message transceiver module 2001 and an execution
module 2002.
[0191] The message transceiver module 2001 is configured to receive
a message, which indicates that a UE is being handed over, sent by
an S-eNB, and transmit the message to the execution module 2002;
and receive a message, which indicates that the UE returns to an
S-eNB service area, sent by the S-eNB when the handover fails, and
transmit the message to the execution module 2002.
[0192] The execution module 2002 is configured to receive the
message, which indicates that the UE is being handed over,
transmitted by the message transceiver module 2001, and buffer an
NAS message to be sent to the UE; and receive the message, which
indicates that the UE returns to the S-eNB service area,
transmitted by the message transceiver module 2001, and send to the
S-eNB the NAS message to be sent to the UE when it is necessary to
send the NAS message to the UE.
[0193] The first type of MME in the EPC according to an embodiment
of the present invention acquires that the UE is being handed over
through receiving the message which indicates that the UE is being
handed over sent by the S-eNB, so as to buffer the NAS message to
be sent to the UE. When the handover fails, the MME receives the
message, which indicates that the UE returns to the S-eNB service
area, sent by the S-eNB, and further sends the NAS message to the
UE through the S-eNB when it is necessary to send the NAS message
to the UE, thereby realizing the effect of correctly sending the
NAS message to the UE when the handover fails.
[0194] The message transceiver module 2001 is further configured to
receive a UE handover complete message sent by the T-eNB when the
handover is successful, and transmit the message to the execution
module 2002. The execution module 2002 is further configured to
receive the UE handover complete message sent by the T-eNB and
transmitted by the message transceiver module when the handover is
successful, and send the NAS message to the UE when it is necessary
to send the NAS message to the UE.
[0195] Therefore, the MME in the EPC according to an embodiment of
the present invention can not only send the NAS message to the UE
correctly through the S-eNB if it is necessary to send the NAS
message to the UE when the handover fails, but also send the NAS
message to the UE correctly through the T-eNB if it is necessary to
send the NAS message to the UE when the handover is successful.
[0196] FIG. 18 is a schematic structural view of a second type of
MME in an EPC according to an embodiment of the present invention.
The MME includes a control module 2101, a retransmission timer
2103, and an execution module 2104.
[0197] The control module 2101 is configured to receive a message,
which indicates that a UE is being handed over, sent by an S-eNB,
and start the retransmission timer 2103; receive a handover
complete message sent by a T-eNB, and stop the retransmission timer
2103.
[0198] The execution module 2104 is configured to send an NAS
message to the S-eNB according to a timing result of the
retransmission timer 2103 when it is necessary to send the NAS
message to the UE after the retransmission timer 2103 expires, and
send the NAS message to the T-eNB when it is necessary to send the
NAS message to the UE after the retransmission timer 2103 is
stopped.
[0199] The second type of MME in the EPC according to an embodiment
of the present invention acquires that the UE is being handed over
through receiving the message which indicates that the UE is being
handed over sent by the S-eNB, and starts the retransmission timer.
When it is necessary to send the NAS message to the UE after the
retransmission timer expires, the MME further sends the NAS message
to the UE through the S-eNB. When the handover is successful, the
MME stops the retransmission timer, and sends the NAS message to
the UE through the T-eNB, thereby realizing the effect of correctly
sending the NAS message to the UE when the handover is successful
or when the handover fails.
[0200] The retransmission timer 2103 may be an S1 interface
application part protocol retransmission timer.
[0201] The message which indicates that the UE is being handed over
received by the control module 2101 contains time information, and
in this case, the MME further includes a calculation control module
2102 configured to resolve the time information and calculate a
time limit of the retransmission timer 2103 according to the time
information, and then transmit the calculating result to the
control module 2101.
[0202] If the message which indicates that the UE is being handed
over contains the time information, the MME may accurately
determine the time limit of the retransmission timer according to
the time information.
[0203] Finally, three eNodeBs provided according to an embodiment
of the present invention are described below in detail. FIG. 19 is
a schematic structural view of a first eNodeB according to an
embodiment of the present invention. The eNodeB includes a
detecting module 2201, a handover processing module 2202, and an
NAS message forwarding module 2203.
[0204] The detecting module 2201 is configured to detect an
abnormal status during a handover of a UE, and send a detecting
result to the handover processing module 2202.
[0205] The handover processing module 2202 is configured to send a
message which indicates that the UE is being handed over to an EPC;
and send to the EPC a message about a service area where the UE
currently belongs to according to a detecting result sent by the
detecting module 2201 when the handover of the UE fails.
[0206] The NAS message forwarding module 2203 is configured to
receive the NAS message sent by the EPC and forward the NAS message
to the UE.
[0207] In practical applications, the eNodeB may be an S-eNB or a
T-eNB depending upon the specific application situation. Therefore,
the first eNodeB provided according to an embodiment of the present
invention includes the functions of both the S-eNB and the
T-eNB.
[0208] The first eNodeB provided according to an embodiment of the
present invention sends to the EPC the message about the service
area where the UE currently belongs to when the handover fails, so
as to enable the EPC to correctly send the NAS message to the UE
according to the above message.
[0209] In practical applications, the eNodeB may be an S-eNB or a
T-eNB depending upon the specific application situation. Therefore,
the first eNodeB provided according to an embodiment of the present
invention includes the functions of both the S-eNB and the
T-eNB.
[0210] FIG. 20 is a schematic structural view of a second eNodeB
according to an embodiment of the present invention. The eNodeB
includes a detecting module 2301, a time information module 2302, a
handover processing module 2303, and an NAS message forwarding
module 2304.
[0211] The detecting module 2301 is configured to detect an
abnormal status during handover of a UE, and send a detecting
result to the handover processing module 2303.
[0212] The time information module 2302 is configured to send time
information corresponding to the handover of the UE to the handover
processing module 2303 according to a processing result of the
handover processing module 2303.
[0213] The handover processing module 2303 is configured to send a
message which indicates that the UE is being handed over to an EPC,
contain the time information provided by the time information
module 2302 in the message which indicates that the UE is being
handed over; and send to the EPC a message about a service area
where the UE currently belongs to according to a detecting result
sent by the detecting module 2301 when the handover of the UE
fails. The handover processing module 2303 includes a handover
execution module 2305 and a UE position processing module 2306. The
handover execution module 2305 is configured to send a message
which indicates that the UE is being handed over to the EPC, and
contain the time information provided by the time information
module 2302 in the message which indicates that the UE is being
handed over. The UE position processing module 2306 is configured
to send to the EPC a message about a service area where the UE
currently belongs to according to the detecting result sent by the
detecting module 2301 when the handover of the UE fails.
[0214] The NAS message forwarding module 2304 is configured to
receive the NAS message sent by the EPC, and forward the NAS
message to the UE.
[0215] The second eNodeB according to an embodiment of the present
invention contains the time information in the message, which
indicates that the UE is being handed over, sent to the EPC, so as
to enable the EPC to determine a time limit of the retransmission
timer according to the time information, thereby sending the NAS
message correctly when the handover of the UE fails after the
retransmission timer expires.
[0216] FIG. 21 is a schematic structural view of a third eNodeB
according to an embodiment of the present invention. The eNodeB
includes a message transceiver module 2401 and an NAS message
processing module 2402.
[0217] The message transceiver module 2401 is configured to receive
an NAS message to be sent to a UE by an EPC, send an X2 interface
control protocol message containing the NAS message in the NAS
message processing module to another NodeB, or send the received
NAS message to another NodeB via a tunnel; receive the NAS message
sent by another eNodeB by using an X2 interface control protocol
message or a tunnel, and send the received NAS message to the
UE.
[0218] The NAS message processing module 2402 is configured to bear
the NAS message received by the message transceiver module 2401 in
the X2 interface control protocol message.
[0219] The third eNodeB provided according to an embodiment of the
present invention bears the NAS message in the X2 interface control
protocol message, and forwards the NAS message between eNodeBs by
using the X2 interface control message, or forwards the NAS message
via a tunnel established between the eNodeBs, thereby providing a
specific implementation manner for forwarding the NAS message at
the X2 interface.
[0220] The third eNodeB according to an embodiment of the present
invention further includes a tunnel establishing module 2403
configured to receive a user plane IP address and a tunnel end
point identifier corresponding to another eNodeB, and send a user
plane IP address and a tunnel end point identifier corresponding to
the third eNodeB itself to the other eNodeB, thereby establishing
an NAS forwarding tunnel or a user data transmitting tunnel between
the third eNodeB itself and the other eNodeB.
[0221] If more than one user data transmitting tunnel is
established, the third eNodeB provided according to an embodiment
of the present invention further includes a tunnel selecting module
2404 configured to select one tunnel from the established user data
transmitting tunnels to forward the NAS message. The eNodeB further
includes a label adding module 2405 configured to add a label to
the NAS message when the NAS message is sent to another eNodeB via
the established user data transmitting tunnel. The addition of the
label aims at enabling the eNodeB to correctly identify the
received NAS message when the NAS message and the user data share
the user data transmitting tunnel.
[0222] The third eNodeB provided according to an embodiment of the
present invention further includes a backup module 2406 configured
to make a backup of the NAS message to be sent to the UE received
by the message transceiver module 2401. By adding the backup module
2405, if the handover fails, the eNodeB can send the backup of the
NAS message to the UE.
[0223] The three eNodeBs provided in an embodiment of the present
invention respectively includes the functions of the eNodeB serving
as both an S-eNB and a T-eNB.
[0224] FIG. 22 is a schematic structural view of an MME according
to an embodiment of the present invention. The MME includes a
message sending module 2501 and a message receiving module
2502.
[0225] The message sending module 2501 is configured to enable an
EPC to send a direct-transfer message to an S-eNB, and the
direct-transfer message contains an NAS message to be sent by the
EPC to a UE.
[0226] The message receiving module 2502 is configured to enable
the EPC to receive a message, which indicates that the UE is being
handed over, sent by the S-eNB, and the message which indicates
that the UE is being handed over is a direct transfer failure
message or direct transfer response message containing a cause
value and an NAS message that fails to be sent.
[0227] Furthermore, the MME further includes a timer start module
2503 and a timer stop module 2504.
[0228] The timer start module 2503 is configured to enable the EPC
to start a retransmission timer. At this time, the message sending
module 2501 is configured to enable the EPC to send the NAS message
to the UE through the S-eNB when it is necessary to send the NAS
message to the UE after the retransmission timer expires if the
handover fails.
[0229] The timer stop module 2504 is configured to enable the EPC
to receive a handover complete message sent by a T-eNB, and stop
the retransmission timer. At this time, the message sending module
2501 is configured to enable the EPC to send the NAS message to the
UE through the T-eNB when it is necessary to send the NAS message
to the UE.
[0230] Through the method and the apparatus for NAS message
processing during handover in an evolved network provided according
to the embodiments of the present invention, an EPC is notified
that the UE is currently being handed over, so that the EPC buffers
an NAS message to be sent to the UE. If the handover fails, the
S-eNB sends a message which indicates that the UE returns to an
S-eNB service area to the EPC, so as to enable the EPC to send the
NAS message to the UE correctly. Alternatively, a retransmission
timer is set, and the EPC is notified that the UE is currently
being handed over, so that the EPC starts the retransmission timer.
If the handover fails, the EPC may send the NAS message to the UE
correctly through the S-eNB after the retransmission timer expires.
If the handover is successful, the EPC may stop the retransmission
timer and send the NAS message to the UE through the T-eNB.
Alternatively, the NAS message is forwarded to the T-eNB via an X2
interface control protocol or a tunnel, thereby providing specific
implementation for forwarding the NAS message via the X2
interface.
[0231] The above descriptions are merely exemplary embodiments of
the present invention, and not intended to limit the scope of the
present invention. Any modification, equivalent replacement, or
improvement made without departing from the spirit and principle of
the present invention should fall within the scope of the present
invention.
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